1. Field of the Invention
This invention relates to an automatic transmission for a motor vehicle that includes planetary gearsets and clutches and brakes whose state of engagement and disengagement determines speed ratios produced by the transmission.
2. Description of the Prior Art
In a front wheel drive vehicle, the axial space available for the transmission is limited by the width of the engine compartment and the length of the engine. In addition, the trend to increase the number of ratios available generally increases the number of components required. For these reasons, it is desirable to position components concentrically in order to minimize axial length. The ability to position components concentrically is limited, however, by the need to connect particular components mutually and to the transmission case.
Furthermore, it is desirable for the output element to be located near the center of the vehicle, which corresponds to the input end of the gear box. An output element located toward the outside of the vehicle may require additional support structure and add length on the transfer axis. With some kinematic arrangements, however, the need to connect certain elements to the transmission case requires that the output element be so located.
For example, the support for the A clutch and B clutch is located at the front of the transmission and must be driven in rotation by the ring gear of a front planetary gearset. Each clutch requires a balance dam to cancel the effects of centrifugal force on pressure in the clutch's servo piston. In current designs it is conventional that hydraulic fluid is supplied to each balance volume through a separate feed passage. But a need exists for a technique that would connect the balance volume of each clutch piston to a source of pressurized hydraulic fluid through a single feed passage, such as fluid passage formed in the clutch support.